I've come across various scenarios. One example is javax.swing.tree.DefaultMutableTreeNode. It has numerous methods that return Enumerations, including: - children - depthFirstEnumeration - breadthFirstEnumeration - preorderEnumeration - postorderEnumeration - pathFromAncestorEnumeration
I've created a utility class with methods to return Iterables for each of these types of Enumerations for convenience, but it would be much nicer to just use a method reference. Deque's descendingIterator() method is a more modern good candidate for treating as an Iterable. See this question on StackOverflow: http://stackoverflow.com/questions/3883131/idiomatic-way-to-use-for-each-loop-given-an-iterator -- Colin On Wed, Aug 24, 2011 at 5:45 PM, Ben Evans <benjamin.john.ev...@gmail.com>wrote: > Hi Dan, > > On Wed, Aug 24, 2011 at 7:10 PM, Dan Smith <daniel.sm...@oracle.com> > wrote: > > > I was pointed to some comments on core-libs about adapting Enumerations > to > > for loops in SE 8. (Sorry for the new thread -- I wasn't subscribed.) > It > > turns out lambdas + extension methods will make this very easy. > > > > In the API: > > > > interface Enumeration<E> extends Iterator<E> { > > boolean hasMoreElements(); > > E nextElement(); > > boolean hasNext() default #hasMoreElements; > > E next() default #nextElement; > > void remove() default { throw new UnsupportedOperationException(); } > > } > > > > Note that Iterable is a function type -- a thunk producing an Iterator -- > > and so we can express Iterables with lambdas and method references. It's > > becoming clear that a for loop should provide a target type for these > > things, so that will probably be part of the SE 8 feature set. > > > > With a method reference: > > > > Hashtable<String,Object> h = …; > > for (String s : h#keys) { … } > > > > I'm struggling to see where this might be useful. This example is obviously > too trivial and would add nothing, but I can't see to come up with any more > extensive example where having a method reference in this position would be > actually useful. > > Can someone else provide a more compelling example for a for loop taking a > method reference? > > Thanks, > > Ben > >
